Quality Control of High Performance Superconductor Tapes

ABSTRACT

A superconductor tape and method for manufacturing, measuring, monitoring, and controlling same are disclosed. Embodiments are directed to a superconductor tape which includes a superconductor film overlying a buffer layer which overlies a substrate. In one embodiment, the superconductor film is defined as having a c-axis lattice constant higher than 11.74 Angstroms. In another embodiment, the superconductor film comprises BaMO3, where M=Zr, Sn, Ta, Nb, Hf, or Ce, and which has a (101) peak of BaMO3 elongated along an axis that is between 60° to 90° from an axis of the (001) peaks of the superconductor film. These and other embodiments achieve well-aligned nanocolumnar defects and thus a high lift factor, which can result in superior critical current performance of the tape in, for example, high magnetic fields.

CROSS REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. patent application Ser. No.16/329,658, filed on Feb. 28, 2019, issuing on Jul. 19, 2022 as U.S.Pat. No. 11,393,970, which is a 371 application of PCT/US2017/049087,filed on Aug. 29, 2017, which claims priority to U.S. provisional patentapplication No. 62/381,369, filed on Aug. 30, 2016, all of which arehereby incorporated herein by reference in their entireties.

GOVERNMENT SPONSORSHIP

Office of Naval Research Award N00014-14-1-0182.

FIELD OF THE DISCLOSURE

The embodiments disclosed herein are in the field of superconductortapes. More particularly, the embodiments disclosed herein relate tosuperconductor tapes and methods for manufacturing, measuring,monitoring, and controlling same, which, inter alia, achievewell-aligned nanocolumnar defects and thus a high lift factor, which canresult in superior critical current performance of the tape in, forexample, high magnetic fields.

BACKGROUND

Several materials systems are being developed to solve the loomingproblems with energy generation, transmission, conversion, storage, anduse. Superconductors are quite likely a unique system that provides asolution across a broad spectrum of energy problems. Superconductorsenable high efficiencies in generators, power transmission cables,motors, transformers and energy storage. Further, superconductorstranscend applications beyond energy to medicine, particle physics,communications, and transportation. Superconducting tapes have come ofage, enabled by a novel approach to create epitaxial,single-crystal-like thin films on polycrystalline substrates. In thistechnique, a thin film of materials with rock-salt crystal structuresuch as MgO is deposited by ion beam-assisted deposition over flexible,polycrystalline substrates.

Superconducting films that are processed by this technique exhibitcritical current densities comparable to that achieved in epitaxialfilms grown on single crystal substrates. Using this technique, severalinstitutions have demonstrated pilot-scale manufacturing ofsuperconducting composite tapes. It is quite remarkable that currently asingle crystal-like epitaxial film may be manufactured to over a lengthof a kilometer using a polycrystalline substrate base.

However, there are certain drawbacks to today's superconductor tapes.The current carrying capability of superconductors rapidly diminishes ina magnetic field, which poses a problem for their use in applicationssuch as wind generators where the generator coil would be subjected tomagnetic fields of a few Tesla. Additionally, since superconductivity inhigh-temperature superconductors (HTSs) is localized within their Cu—Oplanes, HTS materials exhibit strong anisotropic behavior. Thisanisotropy is evident in critical current measurements when a magneticfield is aligned at different angles to the film surface (FIG. 1A). Asshown in FIG. 1A, the critical current of a standard HTS tape dropsrapidly as the field is moved away from the film surface and reaches alow value when the field is oriented perpendicular to the tape, which isthe limiting value in coils constructed with these tapes.

Pinning improvement strategies for practical superconductors have beenactively developed over the last decade to improve in-field performance.The most explored approach has been to introduce defects into thesuperconductor that are comparable in lateral dimensions tosuperconducting coherence length. In 2G HTS tapes, such defects includeoxygen vacancies, threading dislocations, twin planes, impurity atoms,irradiation-induced columnar defects, and nanostructured inclusions ofvarious composition and structure.

Recently, to improve pinning, researchers developed an approach forcolumnar defect formation based on chemically doping the superconductingfilm with BaMO₃ (M=Zr, Sn, Hf, Nb, Ce, Ta, etc.). The BZO and BaSnO₃(BSO) inclusions form nano-sized columns, about 5 nm in diameter, by aself-assembly process during superconductor film growth andsignificantly improve the pinning strength. FIG. 1B displays a crosssectional microstructure of a (Gd,Y)Ba₂Cu₃O_(x) (Gd-YBCO)superconducting film grown by MOCVD with abundant self-assembled BaZrO₃(BZO) nanocolumnar defects, mostly oriented perpendicular to the filmplane. Films with such a microstructure exhibit two-fold improvedperformance in a magnetic field at 77 K, especially in orientationsalong the direction of the BZO nanocolumns and result in a loweranisotropy, as shown in FIG. 1A.

Furthermore, research demonstrated that a higher level of Zr additionled to more favorable properties in magnetic fields at low temperatures.In particular, the ‘lift factor,’ which is the ratio of critical currentof the tape in applied magnetic field at low temperature to the criticalcurrent of the tape at 77 K in zero magnetic field, was found to beincreased in tapes with higher levels of Zr content. It was alsorecently shown that high critical current density can be achieved inRE-Ba—Cu—O (REBCO, RE=rare earth) tapes with high levels of Zr addition,even at 77 K. This achievement opened the possibility of combining liftfactor at low temperatures in magnetic fields with high critical currentdensity at 77 K to reach very high critical currents at the lowtemperatures in magnetic fields of interest to many applications.However, it has since been discovered that REBCO tapes with high levelsof Zr addition do not always lead to high lift factors at lowertemperatures in magnetic fields. In essence, for REBCO tapes with highlevels of Zr addition, the lift factor at lower temperatures in magneticfields has been found to be inconsistent. Accordingly, there is need inthe art for superconducting tapes that can consistently achievesubstantially high critical currents at lower temperatures in magneticfields.

SUMMARY

Embodiments are directed to a superconductor tape comprising: asubstrate; a buffer layer overlying the substrate; and a superconductorfilm overlying the buffer layer. The superconductor film is defined ashaving a c-axis lattice constant higher than 11.74 Angstroms.

In an embodiment, the superconductor film (or the tape in general) isover 10 meters in length.

In an embodiment, the superconductor film comprises 5 to 30 mol % ofdopant selected from the group consisting of Zr, Sn, Ta, Nb, Hf, Ce, anda combination thereof.

In an embodiment, the superconductor film comprises BaMO₃, where M=Zr,Sn, Ta, Nb, Hf, or Ce, and which has a (101) peak of BaMO₃ elongatedalong an axis that is between 60° to 90° from an axis of the (001) peaksof the superconductor film.

Embodiments are also directed to a superconductor tape comprising: asubstrate; a buffer layer overlying the substrate; and a superconductorfilm overlying the buffer layer. The superconductor film comprisesBaMO₃, where M=Zr, Sn, Ta, Nb, Hf, or Ce, and which has a (101) peak ofBaMO₃ elongated along an axis that is between 60° to 90° from an axis ofthe (001) peaks of the superconductor film.

In an embodiment, the (101) peak of BaMO₃ is measured by X-raydiffraction.

In an embodiment, the superconductor film (or the tape in general) isover 10 meters in length.

In an embodiment, the superconductor film comprises 5 to 30 mol % ofdopant selected from the group consisting of Zr, Sn, Ta, Nb, Hf, Ce, anda combination thereof.

In an embodiment, the superconductor film is defined as having a c-axislattice constant higher than 11.74 Angstroms.

Embodiments are further directed to a superconductor tape comprising: asubstrate; a buffer layer overlying the substrate; and a superconductorfilm overlying the buffer layer. The superconductor film comprisesBaMO₃, where M=Zr, Sn, Ta, Nb, Hf, or Ce, and which has a (101) peak ofBaMO₃ located at a 2 theta angle higher than 30° when measured by X-rayDiffraction using copper k alpha radiation.

In an embodiment, the superconductor film comprises 5 to 30 mol % ofdopant selected from the group consisting of Zr, Sn, Ta, Nb, Hf, Ce, anda combination thereof.

In an embodiment, the superconductor film is defined as having a c-axislattice constant higher than 11.74 Angstroms.

Embodiments are yet further directed to a superconductor tapecomprising: a substrate; a buffer layer overlying the substrate; and asuperconductor film overlying the buffer layer. The superconductor filmcomprises BaMO₃, where M=Zr, Sn, Ta, Nb, Hf, or Ce, and which has a(101) peak of BaMO₃ located at a 2 theta angle less than 2.6° from the(103) peak of the superconductor phase when measured by X-rayDiffraction using copper k alpha radiation.

In an embodiment, the superconductor film comprises 5 to 30 mol % ofdopant selected from the group consisting of Zr, Sn, Ta, Nb, Hf, Ce, anda combination thereof.

In an embodiment, the superconductor film is defined as having a c-axislattice constant higher than 11.74 Angstroms.

Embodiments are yet further directed to a method of measuring a c-axislattice parameter of a superconductor film in a superconductor tape. Themethod comprises providing a superconductor tape comprising: asubstrate; a buffer layer overlying the substrate; and a superconductorfilm deposited over the buffer layer. The method also comprisesmeasuring the c-axis lattice parameter of the superconductor film viain-line X-ray Diffraction in real-time during deposition of thesuperconductor film over the buffer layer.

In an embodiment, the step of measuring is performed subsequentdeposition of the superconductor film.

In an embodiment, the superconductor film (or the tape in general) isover 10 meters in length.

In an embodiment, the superconductor film comprises 5 to 30 mol % ofdopant selected from the group consisting of Zr, Sn, Ta, Nb, Hf, Ce, anda combination thereof.

In an embodiment, the c-axis lattice parameter is a c-axis latticeconstant higher than 11.74 Angstroms.

In an embodiment, the superconductor film comprises BaMO₃, where M=Zr,Sn, Ta, Nb, Hf, or Ce, and which has a (101) peak of BaMO₃ elongatedalong an axis that is between 60° to 90° from an axis of the (001) peaksof the superconductor film.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description,will be better understood when read in conjunction with the appendeddrawings. For the purpose of illustration only, there is shown in thedrawings certain embodiments. It's understood, however, that theinventive concepts disclosed herein are not limited to the precisearrangements and instrumentalities shown in the figures.

FIG. 1A is a plot illustrating anisotropy in critical current ofMOCVD-based HTS tape with and without self-assembled BaZrO₃ (BZO)nanocolumns.

FIG. 1B is a diagram illustrating cross-sectional microstructures of aZr-doped superconducting film synthesized by MOCVD, showing abundantnanocolumnar defects of self-assembled BZO.

FIG. 2A is a diagram illustrating a cross-sectional TEM analysis of aZr-added (Gd,Y)BCO tape with a low lift factor in I_(c) at 30 K, 2.5 T,showing not well-aligned, discontinuous BZO nanocolumns perpendicular tothe tape plane.

FIG. 2B is a diagram illustrating a cross-sectional TEM analysis of aZr-added (Gd,Y)BCO tape with a high lift factor in I_(c) at 30 K, 2.5 T,exhibiting strongly-aligned, continuous BZO nanocolumns.

FIG. 3A is a plot illustrating (007) peaks of the REBCO phase of severalZr-doped (Gd,Y)BCO tapes with increasing levels of (Ba+Zr)/Cu content,as measured by X-ray Diffraction using copper K-alpha (Cu K-α)radiation.

FIG. 3B is a table illustrating the (Ba+Zr)/Cu composition of the REBCOtapes referenced in the plot of FIG. 3A.

FIG. 4 is a plot illustrating a c-axis lattice parameter of severalZr-doped (Gd,Y)BCO tapes with increasing levels of (Ba+Zr)/Cu content,as measured by X-ray Diffraction.

FIG. 5 is a plot illustrating dependence of the lift factor in criticalcurrent at 30 K of several Zr-doped (Gd,Y)BCO tapes with increasingvalues of c-axis lattice parameter, as measured by X-ray Diffraction.

FIG. 6 is a plot illustrating (101) peaks of BZO of several Zr-doped(Gd,Y)BCO tapes with increasing levels of (Ba+Zr)/Cu content, asmeasured by X-ray Diffraction using Cu K-α radiation.

FIG. 7 is a plot illustrating the angular distance between the peaklocations of the BZO (101) peak and (103) peak of the REBCO phase ofseveral Zr-doped (Gd,Y)BCO tapes with increasing levels of (Ba+Zr)/Cucontent, as measured by X-ray Diffraction using Cu K-α radiation.

FIG. 8 is a plot illustrating the lift factor in critical current at 30K, 3 T with changing angular distance between the peak locations of theBZO (101) peak and (103) peak of the REBCO phase of several Zr-doped(Gd,Y)BCO tapes with increasing levels of (Ba+Zr)/Cu content, asmeasured by X-ray Diffraction using Cu K-α radiation.

FIG. 9A is a plot illustrating two-dimensional (2D) X-ray Diffraction(XRD) data from Zr-added (Gd,Y)BCO tapes with strongly-aligned, long BZOnanocolumns exhibiting a high lift factor in critical current at 30 K, 3T.

FIG. 9B is a plot illustrating two-dimensional (2D) XRD data fromZr-added (Gd,Y)BCO tapes with not well-aligned, short BZO nanocolumnsexhibiting a low lift factor in critical current at 30 K, 3 T.

FIG. 10 is a perspective view of a schematic diagram illustrating anin-line X-ray diffraction unit to measure the c-axis lattice parameteras a superconductor tape is being fabricated.

FIG. 11 is a plot illustrating shift of a (007) peak of REBCO tapes withdifferent (Ba+Zr)/Cu content from theta-2 theta scans using the in-lineXRD tool using Cu K-α radiation.

FIG. 12 is a plot illustrating correlation between the c-axis latticeconstants of REBCO films with different (Ba+Zr)/Cu content and theintensity of RE₂O₃ peaks of the films, as measured by X-ray Diffractionusing Cu K-α radiation.

FIG. 13 is a flowchart illustrating an embodiment of a method ofmeasuring a c-axis lattice parameter of a superconductor film in asuperconductor tape, in accordance with an embodiment.

FIG. 14 is a perspective schematic and cross-sectional diagramillustrating a microstructure of an ultra-thin film high-temperaturesuperconducting tape, in accordance with an embodiment.

DETAILED DESCRIPTION

Heavy-doping of REBCO films is necessary, but not a sufficient enoughcondition to achieve high lift factor in critical current (I_(c)) at lowtemperatures. The inventors have discovered that a strong alignment ofBaMO₃ (M=Zr, Sn, Hf, Nb, Ce, Ta, etc.) nanocolumns along the c-axis ofthe REBCO films is an important condition to achieving high liftfactors. For example, FIGS. 2A and 2B show cross-sectionalmicrostructures of two tapes with the same J_(c) of 3.08 MA/cm² at 77 K,0 T, but with different lift factors in critical currents of 3.85 and6.93 at 30 K, 2.5 T (B∥c). The tape in FIG. 2A has a low lift factor,and it consists of BZO nanocolumns that are not well-aligned and notcontinuous from the buffer layers to the film surface. On the otherhand, the tape in FIG. 2B has a high lift factor and consists ofstrongly-aligned BZO nanocolumns continuous from the buffer layers tothe film surface. The inventors have discovered that the microstructuraldifference shown in FIG. 2A-2B is the culprit behind the large scatterin the critical current of doped GdYBCO tapes at 30 K, 3 T. Accordingly,along with the Zr-doping, a strong alignment of BZO nanocolumns alongthe c-axis of the REBCO films is critical to achieve consistently highlift factors. While the embodiments described herein primarily referenceBZO films, it is understood that the embodiments equally apply to anyBaMO₃ (M=Zr, Sn, Hf, Nb, Ce, Ta, etc.) films.

However, microstructural examination of the alignment of suchnanocolumns in REBCO tapes is a destructive technique and is relegatedto very small areas of a few square micrometers. It is thereforedesirable to provide a nondestructive method that can be used to examinelarger areas of REBCO tapes to verify if the highly-aligned nanocolumnardefects are present. Additionally, there is great value if such methodcan be implemented in-line in the processing of REBCO tapes so that thefeedback from the microstructural analysis can be used in real-time formonitoring and, in turn, control of the process to achieve well-alignednanocolumnar defects and hence superior critical current performance inhigh magnetic fields. By detecting/measuring the BaMO₃ (M=Zr, Sn, Hf,Nb, Ce, Ta, etc.) nanocolumn alignment in real-time duringsuperconductor manufacture, the manufacturing process can be modified toconsistently obtain the required degree of alignment. Examples ofmodification to the manufacturing process are lowering the depositiontemperature and/or increasing the oxygen partial pressure and/orincreasing the barium content in the precursor and/or decreasing thecopper content in the precursor. These and other advantages of thepresent invention will become more fully apparent from the detaileddescription of the invention herein below.

It is to be understood that the figures and descriptions of the presentinvention may have been simplified to illustrate elements that arerelevant for a clear understanding of the present embodiments, whileeliminating, for purposes of clarity, other elements found in a typicalsuperconductor tape or typical method for fabricating, measuring,monitoring, or controlling a superconductor tape. Those of ordinaryskill in the art will recognize that other elements may be desirableand/or required in order to implement the present embodiments. However,because such elements are well known in the art, and because they do notfacilitate a better understanding of the present embodiments, adiscussion of such elements is not provided herein. It is also to beunderstood that the drawings included herewith only provide diagrammaticrepresentations of the presently preferred structures of the presentinvention and that structures falling within the scope of the presentembodiments may include structures different than those shown in thedrawings. Reference will now be made to the drawings wherein likestructures are provided with like reference designations.

Before explaining at least one embodiment in detail, it should beunderstood that the concepts set forth herein are not limited in theirapplication to the construction details or component arrangements setforth in the following description or illustrated in the drawings. Itshould also be understood that the phraseology and terminology employedherein are merely for descriptive purposes and should not be consideredlimiting.

It should further be understood that any one of the described featuresmay be used separately or in combination with other features. Otherembodiments of devices, systems, methods, features, and advantagesdescribed herein will be or become apparent to one with skill in the artupon examining the drawings and the detailed description herein. It'sintended that all such additional devices, systems, methods, features,and advantages be protected by the accompanying claims.

For purposes of this disclosure, the terms “film” and “layer” may beused interchangeably.

Embodiments of the present application are directed to a non-destructivemethod to rapidly qualify the (Ba+Zr)/Cu content of REBCO tapes, whichmay optionally be implemented even in real-time during processing of thetapes as a quality control tool. Additionally, embodiments of thepresent application provide a non-destructive method to qualify theorientation of the nanocolumnar defects of BaMO₃, which determines themagnitude of the lift factor in critical current performance. Therefore,at least one objective of embodiments of the present application is toconsistently achieve a uniformly high critical current in a magneticfield in long lengths of REBCO tapes. Another objective is to develop aquality control (QC) tool to monitor the quality of the REBCO tape insitu during tape fabrication (or after fabrication) so as to enableuniformly high critical current in a magnetic field. Moreover, a keyaspect of embodiments of the present application is the development of anon-destructive, rapid, in-line quality control method that can be usedto determine the quality of the alignment of nanocolumnar defects and,in turn, predict the performance of REBCO tapes in high magnetic fields.

In an embodiment, a nondestructive method based on X-ray Diffraction(XRD) of superconductor tapes is capable of determining the criticalcompositional ratio of Ba, Cu, and dopant on which the critical currentof the tape in a magnetic field depends on. In another embodiment, anXRD method is disclosed that can nondestructively determine the degreeof orientation of nanocolumnar defects in the superconductor film ofsuperconductor tape. In yet another embodiment, an X-ray Diffractionunit in an in-line mode in a superconductor deposition apparatus canobtain real-time information on the compositional ratio of Ba, Cu, anddopant.

FIG. 3A, by way of example only, is a plot illustrating (007) peaks ofthe REBCO phase of several Zr-doped (Gd,Y)BCO tapes with increasinglevels of (Ba+Zr)/Cu content, as measured by XRD using Cu K-α radiation.In other words, FIG. 3A shows the (007) peak from XRD analysis ofZr-added REBCO tapes with different compositions of Ba, Cu, and Zr. FIG.3B, by way of example only, is a table illustrating the (Ba+Zr)/Cucomposition of the REBCO tapes referenced in the plot of FIG. 3A. Asshown in FIGS. 3A-3B, as the (Ba+Zr)/Cu content increases, the (007)peak location shifts to 2 theta values, i.e., the c-axis latticeparameter increases. FIG. 4 , by way of example only, is a plotillustrating a c-axis lattice parameter of several Zr-doped (Gd,Y)BCOtapes with increasing levels of (Ba+Zr)/Cu content, as measured by XRD.The aforementioned trend of increasing c-axis lattice parameter withincreasing content of (Ba+Zr)/Cu in the REBCO tape is clearly shown inFIG. 4 . Specifically, as the (Ba+Zr)/Cu content in the REBCO tape isincreased from 0.53 to 0.84, the c-axis lattice parameter increases from11.72 Å to 11.84 Å. The c-axis lattice parameter increases sharplybeyond 11.74 Å. FIG. 5 , by way of example only, is a plot illustratingthe dependence of the lift factor in critical current of severalZr-doped (Gd,Y)BCO tapes with increasing values of c-axis latticeparameter, as measured by XRD. As shown in FIG. 5 , as the c-axislattice parameter of the REBCO tape increases, the lift factor incritical current at 30 K, 3 T (magnetic field B c-axis) also increases.Hence, the measurement of the c-axis lattice parameter or the shift inthe 2 theta value of a (001) peak of REBCO by XRD is a very goodindicator of the in-field critical current performance of the tape.

While a higher value of (Ba+Zr)/Cu and a higher c-axis lattice parameteris desirable, it does not assure achieving good in-field performance inREBCO tapes. As shown in FIG. 2B, it is also essential that the BZOnanocolumns are well-aligned through the thickness of the REBCO film.Since there is a tendency of the BZO nanocolumns to orient along the a-bplane in heavily-doped films, it is more challenging to assure theuninhibited growth of c-axis-aligned nanocolumns. Minor fluctuations inthe temperature, oxygen partial pressure and incorporation of barium andcopper in the films can perturb the growth of well-aligned nanocolumns.Additionally, it is important to achieve a well-aligned nanocolumngrowth without excessive (Ba+Zr)/Cu and too high a c-axis latticeparameter of REBCO since the critical current at 77 K in zero magneticfield may be reduced. To achieve a high critical current at lowertemperatures in high magnetic fields, it important to achieve a highlift factor as well as good critical current at 77 K in zero magneticfield.

FIG. 6 , by way of example only, is a plot illustrating the (101) peaksof the BZO phase of several Zr-doped (Gd,Y)BCO tapes with increasinglevels of (Ba+Zr)/Cu content, as measured by XRD using Cu K-α radiation.As shown in FIG. 6, as the (Ba+Zr)/Cu content increases, the (101) peaklocation of the BZO phase shifts to higher 2theta values, i.e., itslattice parameter increases. The (101) peak location of the BZO phaseshifts to values higher than 30° for (Ba+Zr)/Cu content greater than0.71.

FIG. 7 , by way of example only, is a plot illustrating the angulardistance between the peak locations of the BZO (101) peak and (103) peakof the REBCO phase of several Zr-doped (Gd,Y)BCO tapes with increasinglevels of (Ba+Zr)/Cu content, as measured by XRD using Cu K-α radiation.As shown in FIG. 7, as the (Ba+Zr)/Cu content increases beyond 0.72, thedistance between the peak locations of the BZO (101) peak and (103) peakof the REBCO phase decreases below 2.6°. In other words, as the(Ba+Zr)/Cu content increases beyond a certain threshold, the latticeparameters of BZO and REBCO phase become closer together.

FIG. 8 , by way of example only, is a plot illustrating the lift factorin critical current at 30 K, 3 T with changing angular distance betweenthe peak locations of the BZO (101) peak and (103) peak of the REBCOphase of several Zr-doped (Gd,Y)BCO tapes with increasing levels of(Ba+Zr)/Cu content, as measured by XRD using Cu K-α radiation. As shownin FIG. 8 , as the angular distance between the peak locations of theBZO (101) peak and (103) peak of the REBCO phase decreases below 2.6°,the lift factor in critical current at 30 K, 3 T increases to values of6 and higher. As the lattice parameters of BZO and REBCO phase becomecloser together, the BZO nanocolumns become better aligned leading tohigher lift factors in critical current.

FIG. 9A, by way of example only, is a plot illustrating 2D XRD data fromZr-added (Gd,Y)BCO tapes with strongly-aligned, long BZO nanocolumnsexhibiting a high lift factor in critical current at 30 K, 3 T. As shownin FIG. 9A, the BZO (101) peak in the REBCO film with stronglyc-axis-aligned BZO nanocolumns is found to streak or elongate in adirection nearly perpendicular to the (001) peaks of the REBCO phase. Ingeneral, the elongation of the BZO (101) peak is along a direction thatis between 60° and 90° from the axis of the (001) REBCO peaks. The REBCO(103) peak itself is shifted towards smaller 2theta values and thereforecloser to the BZO (101) peak. These two features are not seen in theZr-added (Gd,Y)BCO tapes with not well-aligned BZO nancolumns exhibitinga low lift factor in critical current at 30 K, 3 T, as illustrated inFIG. 9B. The BZO (101) peak is elongated along a constant 2 theta arc,which is aligned at an angle less than 60° from the axis of the (001)REBCO peaks.

FIG. 10 , by way of example only, is a perspective view of a schematicdiagram illustrating an in-line X-ray diffraction (XRD) unit/tool thatcan measure the c-axis lattice parameter as a superconductor tape isbeing fabricated. With reference to FIG. 10 , in one embodiment, an XRDunit is placed in-line with a superconductor deposition unit so as tomeasure, in real-time, any shift in the c-axis lattice parameter of theREBCO phase in the superconductor tape as it is being produced. If thec-axis lattice parameter of the superconductor film is monitored duringits deposition, any deviation from the desired threshold value can bedetermined and the process can be re-tuned. The XRD unit consists of anX-ray source using a chromium anode as well as a line (linear) or area(2D) X-ray detector that can instantaneously measure the diffractedX-ray peaks over a 20 range of 39-135 degrees. The X-ray source anddetector are positioned so as to detect the (007) peak of REBCO. As thetape exits the superconductor deposition unit, it enters the XRD unit.The exact 20 position of the (007) peak is obtained at differentlocations along the length of the tape. By monitoring the magnitude ofthe deviation of the (007) peak from the normal location, the shift inthe c-axis lattice parameter can be determined. By continuouslymonitoring the shift in the (007) REBCO peak location, the shift in theREBCO c-axis lattice parameter and hence the (Ba+Zr)/Cu composition ofthe film can be determined over the tape length. This real-time data ofthe REBCO film composition can then be used to adjust the processparameters. For example, the tape temperature, oxygen partial pressureand/or supply of barium and copper precursors can be adjusted inreal-time so as to achieve consistent composition of (Ba+Zr)/Cu, and,consequently, consistent critical current performance. These processparameters can be adjusted to maintain the (Ba+Zr)/Cu composition is theoptimum interval so as to obtain a high lift factor in critical currentas well as good critical current at 77 K in zero applied magnetic field.In another embodiment, the XRD unit can monitor shift in other (001)peaks of REBCO for the same purposes.

FIG. 11 , by way of example only, is a plot illustrating shift of a(007) peak of REBCO tapes with different (Ba+Zr)/Cu content from theta-2theta scans using the in-line XRD unit/tool shown in FIG. 10 . Thedisclosed in-line XRD tool can discern shifts in the (007) peaks ofREBCO films with significantly different (Ba+Zr)/Cu content. As shown inFIG. 11 , the 20 location of the (007) peak of the film shifts towardslower values of 20 (larger lattice parameter) in films with higherlevels of (Ba+Zr)/Cu content. In one embodiment, the 20 angularresolution of the in-line XRD tool can be improved by modifying thelinear detector-to-tape distance and the X-ray optics, such as thenumber of sensors per units length of the linear detector, as needed, sothat subtle changes in (001) peak position can be detected for slightchanges in (Ba+Zr)/Cu composition in the REBCO films.

In another embodiment, the X-ray source and linear detector shown inFIG. 10 can be positioned such that the location of the BMO (101) peakof the superconductor tape is monitored as it is produced in thesuperconductor deposition unit. The exact 20 position of the BMO (101)peak is obtained at different locations along the length of the tape. Bymonitoring the magnitude of the deviation of the BMO (101) peak from thenormal location, the shift in the c-axis lattice parameter can bedetermined. By continuously monitoring the shift in the BMO (101) peaklocation, the (Ba+Zr)/Cu composition of the film can be determined overthe tape length, as per the data shown in FIG. 6 . This real-time dataof the REBCO film composition may then be used to adjust the processparameters, such as tape temperature, oxygen partial pressure and/orsupply of barium and copper precursors in real-time so as to achieveconsistent composition and, consequently, consistent critical currentperformance.

In yet another embodiment, the X-ray source and linear detector shown inFIG. 10 can be positioned such that the locations of the BMO (101) peakand the REBCO (103) peak of the superconductor tape are monitored as thetape is produced in the superconductor deposition unit. The exact 20positions of the BMO (101) peak and the REBCO (103) peak can be obtainedat different locations along the length of the tape. By continuouslymonitoring the magnitude of the difference in the 20 positions of theBMO (101) peak and the REBCO (103) peak, the (Ba+Zr)/Cu composition ofthe film can be determined over the tape length, as per the data shownin FIG. 7 . This real-time data of the REBCO film composition can thenbe used to adjust the process parameters such as tape temperature,oxygen partial pressure and/or supply of barium and copper precursors inreal-time so as to achieve consistent composition and, consequently,consistent critical current performance.

In yet another embodiment, the linear detector shown in FIG. 10 isreplaced with an area two-dimensional (2D) detector. In this case, theBMO (101) peak may tilt away from its 20 arc and towards the REBCO (103)peak, as illustrated in FIG. 9A, continuously as the superconductor tapeis produced in the superconductor deposition unit. The angle of the tiltof the BMO (101) peak from the axis of the REBCO (001) peaks, asillustrated in FIG. 9A, may also be measured continuously. Themanufacturing process parameters, such as tape temperature, oxygenpartial pressure and/or supply of barium and copper precursors, may thenbe adjusted in real-time so as to achieve a tilt of the BMO (101) peakwithin an angle between 60° and 90° from the axis of the REBCO (001)peaks. By this method, a consistent growth of well-aligned BMOnanocolumns may be achieved and, consequently, a consistent criticalcurrent performance may also be achieved.

FIG. 12 , by way of example only, is a plot illustrating the correlationbetween the c-axis lattice constants of REBCO films with different(Ba+Zr)/Cu content, and the intensity of the RE₂O₃ peaks of the films,as measured by XRD. In addition to monitoring the 2 theta peak locationof the (001) peak, the in-line XRD tool can also be utilized to monitorthe peak intensity of the RE₂O₃ peaks along the length of the tape. FIG.12 shows the correlation between the RE₂O₃ peak intensity of tapes withdifferent c-axis lattice constants of the REBCO film. REBCO films withhigher c-axis lattice constants show reduced RE₂O₃ peak intensity.Hence, by monitoring the RE₂O₃ peak intensity with in-line XRD in theprocessing of REBCO tapes, one can determine changes in the (Ba+Zr)/Cucontent in the tapes.

FIG. 14 , by way of example only, is a perspective schematic andcross-sectional diagram illustrating a microstructure of an ultra-thinfilm high-temperature superconductor tape, in accordance with anembodiment. The superconductor tape 1400 comprises: a substrate 1410; abuffer layer 1420 overlying the substrate 1410; and a superconductorfilm 1430 overlying the buffer layer 1420. In one embodiment, thesuperconductor film of FIG. 14 is defined as having a c-axis latticeconstant higher than approximately 11.74 Angstroms. In one embodiment,the superconductor film (or the tape in general) is over 10 meters inlength. In another embodiment, the superconductor film comprises 5 to 30mol % of dopant selected from the group consisting of Zr, Sn, Ta, Nb,Hf, Ce, or a combination thereof. In still another embodiment, thesuperconductor film comprises BaMO₃, where M=Zr, Sn, Ta, Nb, Hf, or Ce,and which has a (101) peak of BaMO₃ elongated along an axis that isbetween 60° to 90° from an axis of the (001) peaks of the REBCOsuperconductor film.

In another embodiment, the superconductor film 1430 of FIG. 14 maycomprise BaMO₃, where M=Zr, Sn, Ta, Nb, Hf, or Ce, and which has a (101)peak of BaMO3 elongated along an axis that is between 60° to 90° from anaxis of the (001) peaks of the REBCO superconductor film. In oneembodiment, the (101) peak of BaMO₃ is measured by XRD. In anotherembodiment, the superconductor film (or the tape in general) is over 10meters in length. In yet another embodiment, the superconductor filmcomprises 5 to 30 mol % of dopant selected from the group consisting ofZr, Sn, Ta, Nb, Hf, Ce, and a combination thereof In still anotherembodiment, the superconductor film is defined as having a c-axislattice constant higher than 11.74 Angstroms.

In yet another embodiment, the superconductor film 1430 of FIG. 14 maycomprise BaMO₃, where M=Zr, Sn, Ta, Nb, Hf, or Ce, and which has a (101)peak of BaMO₃ located at a 2theta angle higher than 30° when measured byX-ray Diffraction using copper k-alpha radiation. In an embodiment, thesuperconductor film comprises 5 to 30 mol % of dopant selected from thegroup consisting of Zr, Sn, Ta, Nb, Hf, Ce, and a combination thereof.In another embodiment, the superconductor film is defined as having ac-axis lattice constant higher than 11.74 Angstroms.

In still another embodiment, the superconductor film 1430 of FIG. 14 maycomprise BaMO₃, where M=Zr, Sn, Ta, Nb, Hf, or Ce, and which has a (101)peak of BaMO₃ located at a 2 theta angle less than 2.6° from the (103)peak of the superconductor phase when measured by XRD using copperk-alpha radiation. In an embodiment, the superconductor film comprises 5to 30 mol % of dopant selected from the group consisting of Zr, Sn, Ta,Nb, Hf, Ce, and a combination thereof. In another embodiment, thesuperconductor film is defined as having a c-axis lattice constanthigher than 11.74 Angstroms.

By way of example only, FIG. 13 is a flowchart of a method 1300 ofmeasuring a c-axis lattice parameter of a superconductor film in asuperconductor tape. In an embodiment, a superconductor tape comprisinga substrate, buffer layer, and superconductor film may be provided(block 1302). The buffer layer overlies the substrate, and thesuperconductor film is deposited over the buffer layer. A c-axis latticeparameter of the superconductor film is measured in real-time viain-line X-ray Diffraction (block 1304) during deposition of thesuperconductor film over the buffer layer. In one embodiment, themeasuring step 1304 is performed subsequent to deposition of thesuperconductor film. In an embodiment, the superconductor film (or thetape in general) is over 10 meters in length. In yet another embodiment,the superconductor film comprises 5 to 30 mol % of dopant selected fromthe group consisting of Zr, Sn, Ta, Nb, Hf, Ce, and a combinationthereof. In another embodiment, the c-axis lattice parameter is a c-axislattice constant higher than 11.74 Angstroms. In an embodiment, thesuperconductor film comprises BaMO₃, where M=Zr, Sn, Ta, Nb, Hf, or Ce,and which has a (101) peak of BaMO₃ elongated along an axis that isbetween 60° to 90° from an axis of the (001) peaks of the REBCOsuperconductor film, or which has a (101) peak of BaMO₃ located at a 2theta angle less than 2.6° from the (103) peak of the superconductorphase when measured by XRD using copper k-alpha radiation.

It is understood that the superconducting film discussed in connectionwith FIG. 14 and FIG. 13 can include one or more of the featuresdiscussed above in connection with those figures. Features in any of theembodiments described above may be employed in combination with featuresin other embodiments described above, and such combinations areconsidered to be within the spirit and scope of the present invention.Moreover, although the embodiments in method 1300 and the structure ofthe superconductor tapes are described above with reference to variouslayers, additional layers may alternatively be implemented in the method1300 as well as the structure of the superconductor tapes described inany of the embodiments above. Furthermore, the method steps in any ofthe embodiments described herein are not restricted to being performedin any particular order. Such alternatives are considered to be withinthe spirit and scope of the present invention, and may therefore utilizethe advantages of the configurations and embodiments described above.The contemplated modifications and variations specifically mentionedabove are considered to be within the spirit and scope of the presentinvention.

It's understood that the above description is intended to beillustrative, and not restrictive. The material has been presented toenable any person skilled in the art to make and use the conceptsdescribed herein, and is provided in the context of particularembodiments, variations of which will be readily apparent to thoseskilled in the art (e.g., some of the disclosed embodiments may be usedin combination with each other). Many other embodiments will be apparentto those of skill in the art upon reviewing the above description. Thescope of the embodiments herein therefore should be determined withreference to the appended claims, along with the full scope ofequivalents to which such claims are entitled. In the appended claims,the terms “including” and “in which” are used as the plain-Englishequivalents of the respective terms “comprising” and “wherein.”

What is claimed is:
 1. A method of measuring a c-axis lattice parameterof a superconductor film in a superconductor tape, the methodcomprising: providing a superconductor tape comprising: a substrate; abuffer layer overlying the substrate; and a superconductor filmdeposited over the buffer layer; measuring the c-axis lattice parameterof the superconductor film via in-line X-ray Diffraction in real-timesubsequent the deposition of the superconductor film over the bufferlayer.
 2. The method of claim 1, wherein the superconductor film is over10 meters in length.
 3. The method of claim 1, wherein thesuperconductor film comprises 5 to 30 mol % of dopant selected from thegroup consisting of Zr, Sn, Ta, Nb, Hf, Ce, and a combination thereof 4.The method of claim 1, wherein the c-axis lattice parameter is a c-axislattice constant higher than 11.74 Angstroms.
 5. The method of claim 1,wherein the superconductor film comprises BaMO₃, where M=Zr, Sn, Ta, Nb,Hf, or Ce, and which has a (101) peak of BaMO3 elongated along an axisthat is between 60° to 90° from an axis of the (001) peaks of thesuperconductor film.
 6. The method of claim 1, wherein thesuperconductor film comprises BaMO₃, where M=Zr, Sn, Ta, Nb, Hf, or Ce,and which has a (101) peak of BaMO₃ located at a 2 theta angle higherthan 30° when measured by X-ray Diffraction using copper k alpharadiation.
 7. The method of claim 1, wherein the superconductor filmcomprises BaMO3, where M=Zr, Sn, Ta, Nb, Hf, or Ce, and which has a(101) peak of BaMO₃ located at a 2 theta angle less than 2.6° from the(103) peak of the superconductor phase when measured by X-rayDiffraction using copper k alpha radiation.
 8. A method of measuring the(101) X-ray Diffraction peak of BaMO₃ in a superconductor film in asuperconductor tape, the method comprising: providing a superconductortape comprising: a substrate; a buffer layer overlying the substrate;and a superconductor film deposited over the buffer layer; wherein thesuperconductor film comprises BaMO₃, where M=Zr, Sn, Ta, Nb, Hf, or Ce;and measuring the (101) X-ray Diffraction peak of BaMO₃ via in-lineX-ray Diffraction in real-time subsequent the deposition of thesuperconductor film over the buffer layer.
 9. The method of claim 8,wherein the superconductor film is over 10 meters in length.
 10. Themethod of claim 8, wherein the superconductor film comprises 5 to 30 mol% of dopant selected from the group consisting of Zr, Sn, Ta, Nb, Hf,Ce, and a combination thereof
 11. The method of claim 8, wherein thesuperconductor film is defined as having a c-axis lattice constanthigher than 11.74 Angstroms.
 12. The method of claim 8, wherein thesuperconductor film comprises BaMO₃, where M=Zr, Sn, Ta, Nb, Hf, or Ce,and which has a (101) peak of BaMO₃ elongated along an axis that isbetween 60° to 90° from an axis of the (001) peaks of the superconductorfilm.
 13. The method of claim 8, wherein the superconductor filmcomprises BaMO₃, where M=Zr, Sn, Ta, Nb, Hf, or Ce, and which has a(101) peak of BaMO₃ located at a 2 theta angle higher than 30° whenmeasured by X-ray Diffraction using copper k alpha radiation.
 14. Themethod of claim 8, wherein the superconductor film comprises BaMO₃,where M=Zr, Sn, Ta, Nb, Hf, or Ce, and which has a (101) peak of BaMO₃located at a 2 theta angle less than 2.6° from the (103) peak of thesuperconductor phase when measured by X-ray Diffraction using copper kalpha radiation.
 15. A method of measuring the X-ray Diffraction peak ofRE₂O₃ in a superconductor film in a superconductor tape, the methodcomprising: providing a superconductor tape comprising: a substrate; abuffer layer overlying the substrate; and a superconductor filmdeposited over the buffer layer; wherein the superconductor filmcomprises RE₂O₃, where RE=rare earth; and measuring the X-rayDiffraction peak of RE₂O₃ via in-line X-ray Diffraction in real-timesubsequent the deposition of the superconductor film over the bufferlayer.
 16. The method of claim 15, wherein the superconductor film isover 10 meters in length.